Method for making lithium ion battery electrode

ABSTRACT

A method for making a lithium ion battery electrode is provided. An electrode material layer including a plurality of electrode active material particles is provided. The electrode material layer includes a surface. A carbon nanotube layer is formed on the surface of the electrode material layer. The carbon nanotube layer consists of carbon nanotubes

RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201110446801.7, filed on Dec. 28, 2011, inthe China Intellectual Property Office, the disclosure of which isincorporated herein by reference. The application is also related tocopending applications entitled, “METHOD FOR MAKIG LITHIUN ION BATTERY”,filed ______ (Atty. Docket No. US42888); “LITHIUM ION BATTERY”, filed______ (Atty. Docket No. US42887); “LITHIUM ION BATTERY ELECTRODE”,filed ______ (Atty. Docket No. US42885); “THIN FILM LITHIUM IONBATTERY”, filed ______ (Atty. Docket No. US44261); “METHOD FOR MAKINGTHIN FILM LITHIUM ION BATTERY”, filed ______ (Atty. Docket No. US44265).

BACKGROUND

1. Technical Field

The present disclosure relates to a method for making lithium ionbattery electrodes.

2. Description of Related Art

A lithium ion battery includes a case, an anode, a cathode, anon-aqueous electrolyte, and a separator. The anode and the cathode areboth lithium battery electrode. The anode, cathode, non-aqueouselectrolyte, and separator are encapsulated in the case. The separatoris located between the anode and the cathode. The anode, cathode andseparator are infiltrated by the non-aqueous electrolyte. The cathodeincludes a cathode current collector and a cathode material layerdisposed on a surface of the cathode current collector. The anodeincludes an anode current collector and an anode material layer disposedon a surface of the anode current collector.

The current collector is used to collect the charge generated by thelithium ion battery during discharge, and to connect to an externalpower source during the recharging of the lithium ion battery. Thecurrent collectors are usually made of metal foils, such as copper foiland aluminum foil. However, the metal foils have a relatively largeweight. The power density is calculated by power/weight. Therefore, alarge weight of the current collector will decrease the power density ofa lithium ion battery. Furthermore, the metal foils may be corroded bythe electrolyte, which decreases the life span of the lithium ionbattery.

What is needed, therefore, is to provide a lithium ion battery electrodehaving high power density and a long life and a method for making thesame.

BRIEF DESCRIPTION OF THE DRAWING

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale, the emphasis instead being placed upon clearlyillustrating the principles of the present embodiments.

FIG. 1 is a schematic side view of an embodiment of a lithium ionbattery electrode.

FIG. 2 is a scanning electron microscope (SEM) photo of an embodiment ofa drawn carbon nanotube film used in the current collector.

FIG. 3 is an SEM photo of an embodiment of a flocculated carbon nanotubefilm used in the current collector.

FIG. 4 is an SEM photo of an embodiment of a pressed carbon nanotubefilm used in the current collector.

FIG. 5 is a schematic top view of an embodiment of a current collector.

FIG. 6 is a schematic top view of another embodiment of a currentcollector.

FIG. 7 is a structural schematic view of a lithium ion batteryelectrode.

FIG. 8 is an SEM image of one embodiment of a lithium ion batteryelectrode.

FIG. 9 is a flowchart for making a lithium ion battery electrodeaccording to one embodiment.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “another,” “an,” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

Referring to FIG. 1, an embodiment of a lithium ion battery electrode 10includes a current collector 12 and at least one electrode materiallayer 14 disposed on at least one surface of the current collector 12.The current collector 12 and the at least one electrode material layer14 can be two separated layers. In one embodiment, the lithium ionbattery electrode 10 includes two electrode material layers 14 and onecurrent collector 12 sandwiched between the two electrode materiallayers 14.

The lithium ion battery electrode 10 can further include a conductingtab 16 electrically connected with the current collector 12. A materialof the conducting tab 16 can be metal. After the conducting tab 16electrically connects with the current collector 12, a protecting layercan be coated on surface of the conducting tab 16 to protect theconducting tab 16 from being corroded by an electrolyte solution. Amaterial of the protecting layer can be polymer. The conducting tab 16is configured to connect the current collector 12 with outside.

The current collector 12 can be a carbon nanotube layer. The carbonnanotube layer includes a plurality of carbon nanotubes uniformlydistributed therein. The carbon nanotubes in the carbon nanotube layercan be combined with each other by van der Waals attractive forcetherebetween. The carbon nanotubes can be disorderly or orderly arrangedin the carbon nanotube layer. The term ‘disorderly’ describes the carbonnanotubes being arranged along many different directions, such that thenumber of carbon nanotubes arranged along each different direction canbe almost the same (e.g. uniformly disordered), and/or entangled witheach other. The term ‘orderly’ describes the carbon nanotubes beingarranged in a consistently systematic manner, e.g., the carbon nanotubesare arranged approximately along a same direction and or have two ormore sections within each of which the carbon nanotubes are arrangedapproximately along a same direction (different sections can havedifferent directions). The carbon nanotubes in the carbon nanotube layercan be single-walled, double-walled, or multi-walled carbon nanotubes.The thickness of the carbon nanotube layer is not limited, and can be ina range from about 0.5 nanometers to about 1 centimeter. In oneembodiment, the thickness of the carbon nanotube layer is in a rangefrom about 1 micron to about 1 millimeter. The carbon nanotube layer caninclude at least one carbon nanotube film. In the carbon nanotube layer,more than one carbon nanotube film can be stacked together.

Referring to FIG. 2, in one embodiment, the carbon nanotube layer caninclude at least one drawn carbon nanotube film. The drawn carbonnanotube film includes a plurality of successive and oriented carbonnanotubes joined end-to-end by van der Waals attractive forcetherebetween. The carbon nanotubes in the carbon nanotube film can besubstantially aligned in a single direction. The drawn carbon nanotubefilm can be formed by drawing a film from a carbon nanotube array thatis capable of having a film drawn therefrom. The plurality of carbonnanotubes in the drawn carbon nanotube film are arranged substantiallyparallel to a surface of the drawn carbon nanotube film. A large numberof the carbon nanotubes in the drawn carbon nanotube film can beoriented along a preferred orientation, meaning that a large number ofthe carbon nanotubes in the drawn carbon nanotube film are arrangedsubstantially along the same direction. An end of one carbon nanotube isjoined to another end of an adjacent carbon nanotube arrangedsubstantially along the same direction, by van der Waals attractiveforce. A small number of the carbon nanotubes are randomly arranged inthe drawn carbon nanotube film, and has a small if not negligible effecton the larger number of the carbon nanotubes in the drawn carbonnanotube film arranged substantially along the same direction. The drawncarbon nanotube film is capable of forming a free-standing structure.The term “free-standing structure” includes, but not limited to, astructure that does not have to be supported by a substrate. Forexample, a free-standing structure can sustain the weight of itself whenit is hoisted by a portion thereof without any significant damage to itsstructural integrity. So, if the drawn carbon nanotube film is placedbetween two separate supporters, a portion of the drawn carbon nanotubefilm, not in contact with the two supporters, would be suspended betweenthe two supporters and yet maintain film structural integrity. Thefree-standing structure of the drawn carbon nanotube film is realized bythe successive carbon nanotubes joined end to end by van der Waalsattractive force.

Some variations can occur in the orientation of the carbon nanotubes inthe drawn carbon nanotube film as can be seen in FIG. 2.Microscopically, the carbon nanotubes oriented substantially along thesame direction may not be perfectly aligned in a straight line, and somecurve portions may exist. It can be understood that a contact betweensome carbon nanotubes located substantially side by side and orientedalong the same direction can not be totally excluded. More specifically,the drawn carbon nanotube film can include a plurality of successivelyoriented carbon nanotube segments joined end-to-end by van der Waalsattractive force therebetween. Each carbon nanotube segment includes aplurality of carbon nanotubes substantially parallel to each other, andjoined by van der Waals attractive force therebetween. The carbonnanotube segments can vary in width, thickness, uniformity and shape.The carbon nanotubes in the drawn carbon nanotube film are alsosubstantially oriented along a preferred orientation. The drawn carbonnanotube film can be a pure structure only including the carbonnanotubes. The thickness of the drawn carbon nanotube film can be in arange from about 0.5 nanometers to about 100 microns. The width andlength of the drawn carbon nanotube film is not limited. When the carbonnanotube layer includes a plurality of drawn carbon nanotube films, anangle between the aligned directions of the carbon nanotubes in at leasttwo drawn carbon nanotube films can be in a range from about 0 degreesto about 90 degrees, for example can be equal to about 0 degrees, 15degrees, 45 degrees, 60 degrees, or 90 degrees.

Referring to FIG. 3, in another embodiment, the carbon nanotube layercan include at least one flocculated carbon nanotube film formed by aflocculating method.

The flocculated carbon nanotube film can include a plurality of long,curved, disordered carbon nanotubes entangled with each other. Thelength of the carbon nanotube film can be greater than 10 centimeters.The carbon nanotubes can be randomly arranged and curved in theflocculated carbon nanotube film. The carbon nanotubes can besubstantially uniformly distributed in the flocculated carbon nanotubefilm. The adjacent carbon nanotubes are acted upon by the van der Waalsattractive force therebetween, thereby forming an entangled structurewith micropores defined therein. Due to the carbon nanotubes in theflocculated carbon nanotube film being entangled with each other, theflocculated carbon nanotube film has excellent durability, and can befashioned into desired shapes with a low risk to the integrity offlocculated carbon nanotube film. The flocculated carbon nanotube filmcan be a free-standing structure due to the carbon nanotubes beingentangled and adhered together by van der Waals attractive forcetherebetween. The thickness of the flocculated carbon nanotube film canrange from about 1 micron to about 1 millimeter. Many of the embodimentsof the carbon nanotube structure are flexible and do not require the useof a structural support to maintain their structural integrity. Theflocculated carbon nanotube film can be a pure carbon nanotube film onlyincluding carbon nanotubes.

Referring to FIG. 4, in further another embodiment, the carbon nanotubelayer can include at least one pressed carbon nanotube film. The pressedcarbon nanotube film can be formed by pressing a carbon nanotube arrayto slant the carbon nanotubes in the carbon nanotube array. The pressedcarbon nanotube film can be a free-standing carbon nanotube film. Thecarbon nanotubes in the pressed carbon nanotube film are arranged alonga same direction, along more than one predetermined differentdirections, or randomly arranged. The carbon nanotubes in the pressedcarbon nanotube film can rest upon each other. Adjacent carbon nanotubesare attracted to each other and combined by van der Waals attractiveforce. An angle between a primary alignment direction of the carbonnanotubes and a surface of the pressed carbon nanotube film is about 0degrees to approximately 15 degrees. In another embodiment, the angle isgreater than 0 degrees less than 15 degrees. The greater the pressureapplied, the smaller the angle obtained. The thickness of the pressedcarbon nanotube film can be in a range from about 1 micron to about 1millimeter. The pressed carbon nanotube film can be pure carbon nanotubefilm only including carbon nanotubes. The length and width of thepressed carbon nanotube film depend on the carbon nanotube array that ispressed. If the length and width of the carbon nanotube array isrelatively large, the pressed carbon nanotube film can have a relativelylarge length and width.

The conducting tab can be electrically connected to the currentcollector 12 by many methods. Referring to FIG. 5, in one embodiment,the carbon nanotubes in the current collector 12 are aligned along thesame direction, the conducting tab 16 can have a strip shape, and theconducting tab 16 can be arranged on the surface of the currentcollector 12 at one side of the current collector 12. The conducting tab16 can be overlapped on the side of the current collector 12. The lengthdirection of the strip shaped conducting tab 16 can be substantiallyperpendicular to the aligned direction of the carbon nanotubes in thecurrent collector 12. The carbon nanotubes have superior conductivityalong the axial direction. Therefore, in this arranged manner, thecharges in the current collector 12 can be rapidly conducted to theconducting tab 16. The conducting tab 16 can have a line shaped contactand connection area with the current collector 12.

Referring to FIG. 6, in another embodiment, the carbon nanotubes aredisorderly arranged or intercrossed with each other in the currentcollector 12 to form a conducting network. The conducting tab 16 canhave a strip shape and only has an end of the strip in contact with thecurrent collector 12. The conducting tab 16 can be electricallyconnected to the current collector 12 through a point contact. In oneembodiment, the current collector 12 includes at least two stacked drawncarbon nanotube films. The carbon nanotubes in the two drawn carbonnanotube films are substantially perpendicular to each other. The carbonnanotubes in the two drawn carbon nanotube films can be substantiallyparallel to the two substantially perpendicular edges of the currentcollector 12. The conducting tab 16 can be arranged at the corner of thecurrent collector 12 formed by the two substantially perpendicularedges.

The electrode material layer 14 can include electrode active material,conductive agent, and adhesive. The electrode active material is acathode active material or an anode active material. If the electrodematerial is a cathode active material, the electrode 10 is a cathode ofa lithium ion battery, which has a thickness of about 10 micrometers toabout 500 micrometers, for example 200 micrometers. If the electrodematerial is anode active material, the electrode 10 is an anode of alithium ion battery, which has a thickness of about 10 micrometers toabout 500 micrometers, for example 100 micrometers. In one embodiment,the electrode 10 is a cathode having a thickness of about 220micrometers. The cathode active material can be lithium manganate(LiMn₂O₄), lithium cobalt oxide (LiCoO₂), lithium nickel oxide (LiNiO₂),or lithium iron phosphate (LiFePO₄). The anode active material can benatural graphite, pyrolysis carbon, or mesocarbon microbeads (MCMB). Theconductive agent can be

acetylene black, carbon fiber or carbon nanotube. The adhesive can bepolyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

In another embodiment, the electrode material layer 14 consists of theelectrode active material and a number of carbon nanotubes, e.g., theelectrode material layer 14 is free of adhesive. The electrode materiallayer 14 can further include acetylene black, carbon fiber, or any otherconductive agent. In the embodiment according to FIGS. 7 and 8, theelectrode material layer 14 only includes electrode active materialparticles 142 and carbon nanotubes 144. A shape of the electrode activematerial particles 142 is not limited, and can be irregular or regular.A diameter of the electrode active material particles 142 is notlimited, and can be less than 15 micron. Referring to FIG. 8, in oneembodiment, the electrode active material particles 142 can be a cathodeactive material, the cathode active material is lithium cobalt oxideparticles having a diameter less than 15 micron. The carbon nanotubes144 are entangled with each other and combined by van der Waalsattractive force therebetween, thereby forming an integral continuousnet structure having a plurality of micropores defined by the carbonnanotubes 144. The plurality of electrode active material particles 142are dispersed in the net like structure and attached on the surface ofthe carbon nanotubes 144. The carbon nanotube 144 is pure, and has noimpurities adhered thereon. The carbon nanotubes 144 in the lithium ionbattery electrode 10 can serve as a conductive material and microporouscarrier to support and fix the electrode active material particles 142.Thus, even without using an adhesive, the lithium ion battery electrode10 can be an integrative stable structure due to the net structurecomposed of the carbon nanotubes 144. The electrode active materialparticles 142 are uniformly distributed in the net structure.Specifically, the electrode active material particles 142 can be adheredon or entangled by the carbon nanotubes, or the electrode activematerial particles 142 can be wrapped by the carbon nanotubes 144. Theelectrode active material particles 142 and the carbon nanotubes 144 arein contact with each other without adhesive therebetween. The electrodeactive material particles 142 and the carbon nanotubes are fixedtogether by van der Waals attractive force therebetween. A length of thecarbon nanotubes 144 can be longer than 200 microns, and the carbonnanotubes 144 can be entangled with each other to form the netstructure. As such, the electrode active material particles 142 can befixed by the net structure, and the electrode material layer 14 is freeof adhesive.

The carbon nanotube layer used as the current collector 12, the carbonnanotube layer has a relatively good conductivity, stable chemical andelectrical stability, and low weight. Therefore, the current collector12 can have a low weight, and the current collector does not corrodeeasily, and thus has a relatively long lifespan. As such, the lithiumion battery electrode 10 has a high power density and long lifespan.

Referring to FIG. 9, a method for making a lithium ion battery electrodeis provided. The method includes the following steps:

S1: providing an electrode material layer including a number ofelectrode active material particles; and

S2: forming a carbon nanotube layer on a surface of the cathode materiallayer.

In step S1, a method for making the electrode material layer is notlimited.

In one embodiment, the electrode material layer is formed by thefollowing steps:

S11: making a carbon nanotube source including a number of carbonnanotubes;

S12: providing an electrode active material including a number ofelectrode active material particles and a solvent;

S13: adding the carbon nanotube source and the electrode active materialinto the solvent, and shaking the solvent with the carbon nanotubesource and the electrode active material with ultrasonic waves; and

S14: separating the carbon nanotube source and the electrode activematerial from the solvent to obtain the electrode material layer.

In step S11, the carbon nanotube source can be made of carbon nanotubes.The carbon nanotubes can be single-walled carbon nanotubes,double-walled carbon nanotubes, or multi-walled carbon nanotubes.Diameters of the carbon nanotubes can be in a range from about 0.5nanometers to about 100 nanometers. The carbon nanotubes can be pure,meaning there is few or no impurities adhered on surface of the carbonnanotubes. In some embodiments, there are no functional groups attachedon the carbon nanotubes. A length of the carbon nanotubes can be thesame or different. The length of the carbon nanotubes can be longer than300 micrometers. In one embodiment, the lengths of the carbon nanotubesare substantially the same. A method for making the carbon nanotubesource can include providing a carbon nanotube array, wherein the carbonnanotube array can be formed on a substrate, and scratching the carbonnanotube array from the substrate to form the carbon nanotube source.The carbon nanotube source obtained directly from the carbon nanotubearray can make the lithium ion battery electrode stronger. In oneembodiment, the carbon nanotube array is a super aligned carbon nanotubearray. A method for making the carbon nanotube array can be CVD method,arc discharge method, aerosol method, or any other appropriate method.

In the step S12, the solvent can be ethanol, glycol, acetone,N-Methyl-2-pyrrolidone, water, or combination thereof. In oneembodiment, the solvent is ethanol. The solvent is contained in acontainer, such as a beaker.

In the step S13, the carbon nanotube source and the electrode activematerial form a mixture. A weight percentage of the carbon nanotubes inthe mixture can be in a range from about 0.1% to about 20%. In someembodiments, the weight percentage of the carbon nanotubes can be in arange from about 1% to about 10%. A power of the ultrasonic wave can bein a range from about 400 W to about 1500 W. In some embodiments, thepower is in a range from about 800 W to about 1000 W. A time of shakingusing ultrasonic waves can range from about 2 minutes to about 30minutes. In some embodiments, the shaking time ranges from about 5minutes to about 10 minutes. The solvent with the carbon nanotube sourceand the electrode active material can be shaken with ultrasonic wavescontinuously or at intervals.

In step S14, after the solvent with the carbon nanotube source and theelectrode active material is shaken, the carbon nanotubes in the carbonnanotube source and the electrode active material particles in theelectrode active material combine with each other to form mixture. Themixture consists of the carbon nanotubes and electrode active materialparticles. The solvent with the mixture is kept still for about 1 minuteto about 20 minutes. The mixture will deposit to a bottom of thesolvent. After the solvent with the carbon nanotube source and theelectrode active material is shaken, the carbon nanotubes entangle witheach other to form a net structure. The electrode active materialparticles are wrapped by the net structure and attached on the surfaceof the carbon nanotubes to form an integrity mixture. The electrodeactive material particles have a larger density than the solvent, and assuch, the integrity mixture can be deposited to the bottom of thesolvent. After the mixture has deposited to the bottom of the solvent,the solvent can be absorbed from the container by a pipe, therebyseparating the mixture from the solvent. After the carbon nanotubesource and the electrode active material are separated from the solvent,the mixture of the carbon nanotube source and the electrode activematerial can be dried at a room temperature or at a temperature fromabout 25 centigrade to about 80 centigrade. After the mixture is dried,the mixture can be cut directly to form the lithium ion batteryelectrode. In other embodiments, the mixture can be pressed and then cutto form the lithium ion battery electrode. The electrode material layermade by the above method consists of carbon nanotubes and electrodeactive material particles.

In step S2, the carbon nanotube layer includes at least one the drawncarbon nanotube film, the flocculated carbon nanotube film and/or thepressed carbon nanotube film. After the drawn carbon nanotube film, theflocculated carbon nanotube film or the pressed carbon nanotube film isformed, it can be laid directly on the surface of the electrode materiallayer. In one embedment, the carbon nanotube layer is one pressed carbonnanotube film. The carbon nanotube layer is formed on the surface of theelectrode material layer by the following steps: S21: proving a carbonnanotube array; S22: transferring the carbon nanotube array to thesurface of the electrode material layer; and S23: pressing the carbonnanotue array.

In step S21, the method for making the carbon nanotube array is nodlimited. In one embodiment, the carbon nanotube array is formed on asubstrate by CVD method.

In the step S22, the carbon nanotube array is transferred on the surfaceof the electrode material layer by covering the substrate with thecarbon nanotube array on the surface of the electrode material layer,wherein the carbon nanotube array is sandwiched between the substrateand the electrode material layer.

In one embodiment, step S23 includes steps of: applying a pressure onthe substrate to press the carbon nanotube array fall onto the surfaceof the electrode material layer; and removing the substrate from thecarbon nanotube array. The substrate can be directly take off from thecarbon nanotube array, and at least part of carbon nanotubes in thecarbon nanotube array stays on the surface of the electrode materiallayer to form the first carbon nanotube layer. In other embodiments, thesubstrate can be removed from the carbon nanotube array by applying athin sheet between the carbon nanotube array and the substrate, and thenthe substrate is removed, the carbon nanotube array stays on the surfaceof the electrode material layer to form the first carbon nanotube layer.After the substrate is removed, the carbon nanotube array staying on thesurface of the electrode material layer can be further pressed.

In other embodiments, step S23 includes removing the substrate from thecarbon nanotube array and pressing the carbon nanotube array. Thesubstrate can be removed by the method previously disclosed. A methodfor pressing the carbon nanotube array can be carried out by applying apressing device on the carbon nanotube array, and pressing the carbonnanotube array with the pressing device. In one embodiment, the pressingdevice can be a pressure head. The pressure head has a smooth surface.The shape of the pressure head and the pressing direction can determinethe direction of the carbon nanotubes arranged therein. When a pressurehead (e.g a roller) is used to travel across and press the array ofcarbon nanotubes along a predetermined single direction, a carbonnanotube layer having a plurality of carbon nanotubes primarily alignedalong a same direction is obtained. There may be some variation in thecarbon nanotube layer. Different alignments can be achieved by applyingthe roller in different directions over an array. Variations in thecarbon nanotube layer can also occur when the pressure head is used totravel across and press the array of carbon nanotubes several times. Thevariation will occur in the orientation of the nanotubes. Variations inpressure can also create different angles between the carbon nanotubesand the surface of the carbon nanotube layer. When a planar pressurehead is used to press the array of carbon nanotubes along the directionperpendicular to the substrate, a carbon nanotube layer having aplurality of carbon nanotubes isotropically arranged can be obtained.When a roller-shaped pressure head is used to press the array of carbonnanotubes along a certain direction, a carbon nanotube layer having aplurality of carbon nanotubes aligned along the certain direction isobtained. When a roller-shaped pressure head is used to press the arrayof carbon nanotubes along different directions, a carbon nanotube filmhaving a plurality of sections having carbon nanotubes aligned alongdifferent directions is obtained.

In another embodiment, the lithium ion battery electrode can be formedby steps of: providing a sheet structure having a surface; providing aslurry including electrode active material, conductive agent, andadhesive; applying the slurry on the surface of the sheet structure by acoating method or a spinning method; forming the carbon nanotube layeron the electrode material layer; solidifying the slurry; and removingthe sheet structure. The sheet structure can be a metal sheet, a glasssheet, or the carbon nanotube layer. If the sheet structure is thecarbon nanotube layer, the steps of forming the carbon nanotube layer onthe electrode material layer and removing the sheet structure can beomitted.

The method for making the lithium ion battery electrode can furtherinclude a step of electrically connecting a conducting tab with thecarbon nanotube layer. The conducting tab can be fixed on a surface ofthe carbon nanotube layer via conductive adhesive.

Finally, it is to be understood that the above-described embodiments areintended to illustrate rather than limit the present disclosure.Variations may be made to the embodiments without departing from thespirit of the present disclosure as claimed. Elements associated withany of the above embodiments are envisioned to be associated with anyother embodiments. The above-described embodiments illustrate the scopeof the present disclosure but do not restrict the scope of the presentdisclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A method for making lithium ion batteryelectrodes comprising: providing an electrode material layer comprisinga plurality of electrode active material particles and having a surface;and forming a carbon nanotube layer on the surface of the electrodematerial layer, wherein the carbon nanotube layer consists of aplurality of carbon nanotubes.
 2. The method of claim 1, wherein amethod for making the electrode material layer comprises: providing acarbon nanotube source comprising a plurality of carbon nanotubes, and asolvent; adding the carbon nanotube source and the plurality ofelectrode active material particles into the solvent, and agitating thesolvent with the carbon nanotube source and the plurality of electrodeactive material particles with ultrasonic waves; and separating thecarbon nanotube source and the plurality of electrode active materialparticles from the solvent to obtain the electrode material layer. 3.The method of claim 2, wherein the carbon nanotube source is made by:providing a substrate and a carbon nanotube array formed on thesubstrate; and scratching the carbon nanotube array from the substrateto form the carbon nanotube source.
 4. The method of claim 2, whereinthe electrode material layer consists of the plurality of electrodeactive material particles and the plurality of carbon nanotubes.
 5. Themethod of claim 2, wherein the solvent is ethanol, glycol, acetone,N-Methyl-2-pyrrolidone, water, or combination thereof.
 6. The method ofclaim 1, wherein the carbon nanotube layer is formed on the surface ofthe electrode material layer by: providing a carbon nanotube array, thecarbon nanotube array comprising a plurality of carbon nanotubes;transferring the carbon nanotube array to the surface of the electrodematerial layer; and pressing the carbon nanotube array.
 7. The method ofclaim 6, wherein the carbon nanotube array is transferred on the surfaceof the electrode material layer by applying the substrate with thecarbon nanotube array on the surface of the electrode material layer,the carbon nanotube array being sandwiched between the substrate and theelectrode material layer.
 8. The method of claim 7, further comprising astep of separating the substrate from the carbon nanotube array.
 9. Themethod of claim 8, wherein the substrate is separated from the carbonnanotube array by applying a thin sheet between the carbon nanotubearray and the substrate.
 10. The method of claim 8, wherein thesubstrate is directly removed from the carbon nanotube array, and atleast a part of the carbon nanotubes of the carbon nanotube arrayremains on the surface of the electrode material layer to form the firstcarbon nanotube layer.
 11. The method of claim 6, wherein the step ofpressing the carbon nanotube array is carried out by: applying apressing device on the carbon nanotube array; and pressing the carbonnanotube array with the pressing device.
 12. The method of claim 1,wherein the electrode active material is an anode active material, andthe lithium ion battery electrode is a lithium ion battery anode. 13.The method of claim 12, wherein the anode active material is selectedfrom the group consisting of natural graphite, pyrolysis carbon, andmesocarbon microbeads (MCMB).
 14. The method of claim 1, wherein theelectrode active material is a cathode active material, and the lithiumion battery electrode is a lithium ion battery cathode.
 15. The methodof claim 14, wherein the cathode active material is selected from thegroup consisting of lithium manganate (LiMn₂O₄), lithium cobalt oxide(LiCoO₂), lithium nickel oxide (LiNiO₂), and lithium iron phosphate(LiFePO₄).
 16. A method for making a lithium battery electrodecomprising: providing a sheet structure having a surface and a slurryincluding an electrode active material, a conductive agent, andadhesive; applying the slurry on the surface of the sheet structure by acoating method or a spinning method to form an electrode material layer;forming the carbon nanotube layer on a surface of the electrode materiallayer; and solidifying the electrode material layer.
 17. The method ofclaim 16, wherein the step of forming the carbon nanotube layer on theelectrode material layer is carried out before the step of solidifyingthe electrode material layer.
 18. The method of claim 16, wherein thestep of solidifying the electrode material layer is carried out beforethe step of forming the carbon nanotube layer on the electrode materiallayer.
 19. The method of claim 18, wherein the carbon nanotube layer isa carbon nanotube array comprising a plurality of carbon nanotubessubstantially perpendicular with a surface of the electrode materiallayer, and after the carbon nanotube array is applied on the surface ofthe electrode material layer, pressing the carbon nanotube array on thesurface of the electrode material layer.